Field of the Invention
The present invention relates to a developing device in a copier, laser beam printer, facsimile, or another equipment using an electrophotographic system and to a process cartridge and image forming apparatus.
Description of the Related Art
An image forming apparatus using an electrophotographic system, such as a copier, visualizes an electrostatic latent image formed on an image bearing member, such as a photosensitive drum, as a toner image at a developing device and then transfers it to a recording medium at a transfer nip portion defined by the photosensitive drum and a transfer roller. After that, the image forming apparatus fixes the toner image on the recording medium at a nip portion in a fixing device. In this way, the image forming apparatus forms the image on the recording medium.
The developing device has a configuration that includes a toner container for accommodating toner (developer), a developing sleeve (developer bearing member) for bearing and conveying the toner, and a regulating blade for making the toner layer on the developing sleeve uniform and controlling a frictional charge of the toner. As the regulating blade, a configuration in which a flexible metallic support member is covered with a blade member made of a rubber elastic material, such as urethane rubber or polyamide resin is used (Japanese Patent Laid-Open No. 2013-222147). With that configuration, endurance of the regulating blade can be improved, and the regulating blade can be made to be in contact with the developing sleeve with a stable contact pressure and charges can be easily supplied from the regulating blade to the toner.
The developing device is equipped with a toner seal member being in contact with the developing sleeve and regulating blade and configured to seal the toner in a longitudinal end portion. Traditionally, the longitudinal end portion of the regulating blade is arranged on the toner seal member, and the regulating blade is pressed to the developing sleeve by the toner seal to prevent the toner from leaking from a gap between the regulating toner and developing sleeve in the longitudinal end portion. However, in that configuration, because the regulating blade is pressed to the developing sleeve by the toner seal, the thickness of the toner layer on the developing sleeve is not uniform. This may lead to unstable image quality, and may cause the developing sleeve to be shaved by the regulating blade.
Another configuration in which a longitudinal end surface of the regulating blade is pressed by the toner seal member is conceived (Japanese Patent No. 3093918). With that configuration, a rise in the contact pressure between the regulating blade and development roller in the vicinity of the toner seal member can be reduced, and the contact pressure of the regulating blade with respect to the development roller in the longitudinal direction can be made uniform. Consequently, the stabilization of image quality and the prevention of shaving of the developing sleeve can be compatible with the prevention of toner leakage.